In order to increase operation speed and to provide a higher degree of integration in semiconductor devices, several attempts have been made to provide a method for manufacturing a semiconductor integrated circuit device wherein dielectric materials are used to separate circuit components so that they may have small stray capacitances.
According to one such method a polycrystalline or amorphous semiconductor film is deposited on an insulator, and the surface thereof is irradiated by an energy beam such as laser beam or electron beam thereof so as to heat only its surface layer, thereby producing a monocrystalline semiconductor film. Thereafter, a MOS field effect transistor (hereinafter referred to as "MOSFET") is produced on the semiconductor film. Thus, an element which has a small stray capacitance is realized with its periphery and its bottom being isolated by a dielectric material.
The main steps of the production process of such a prior art MOSFET are illustrated in FIGS. 1(a) to (i). The manufacturing process is described below:
As shown in FIG. 1(a), a poly-silicon layer 11 of thickness 5,000 .ANG. is deposited on a quartz (SiO.sub.2) substrate 10 by a usual low pressure chemical vapour deposition (hereinafter referred to as "LPCVD"). The product is exposed to the ozidizing atmosphere of 950.degree. C. to form an oxide film (SiO.sub.2) 12 of thickness 500 .ANG., and a nitride film (Si.sub.3 N.sub.4) 13 of thickness 1,000 .ANG. is deposited thereon by a LPCVD method as shown in FIG. 1(b). Thereafter, as shown in FIG. 1(c), the nitride film 13 is patterned through a photolithography process. Subsequently, the product is exposed to the oxidizing atmosphere of 950.degree. C. for a long time so as to oxidize the portions where the nitride film 13 does not exist, and thereafter the nitride film 13 and the oxide film 12 under the film 13 are removed to obtain an island of poly-silicon layer 11 with its periphery and its bottom surrounded by the SiO.sub.2 film 14 as an insulator. However, the poly-silicon layer 11 does not have a crystalline structure capable of producing elements. So, an energy beam such as a laser beam or electron beam is irradiated to the poly-silicon layer 11 so as to melt and recrystallize the same to form a monocrystalline silicon layer, or a polycrystalline silicon layer comprising large crystal particles. This step is shown in FIG. 1(e), wherein the reference numeral 15 designates a recrystallized silicon layer.
Thereafter, the recrystallized silicon layer 15 is used as a substrate to form a MOSFET. The manufacturing process thereof is the same as that of the usual MOSFET. That is, a gate oxide film 16 is formed on the recrystallized silicon layer 15 as shown in FIG. 1(f). Polycrystalline silicon is deposited thereon as shown in FIG. 1(g), and the poly-silicon is patterned to form a poly-silicon gate electrode 17. Subsequently, as shown in FIG. 1(h), the poly-silicon gate electrode 17 is used as a mask for introducing a large number of impurities into the recrystallized silicon layer 15, thereby producing a source region 18 and a drain region 19 in the silicon layer 15. Thereafter, as shown in FIG. 1(i), an oxide film 20 is formed thereon, and the portions of the oxide film 20 above the gate electrode 17, the source region 18, and the drain region 19 are opened to form contact holes. A gate wiring 21, a source wiring 22, and a drain wiring 23 of aluminum are formed on respective regions embedding the contact holes, and a surface protection film 24 is formed thereon to complete a MOSFET.
In this process the semiconductor layer is isolated to form island patterns, but there is no seed to determine the direction of crystallization in the recrystallizing process. The crystal nucleation occurs at random both timewise and positionally, depending on the temperature distribution that is determined by the power distribution of the laser or electron beam and the material, and it is only possible to control the direction of generation of crystal grains (refer to Japanese Laid Open Patent Publication No. Sho. 58-192381). A pattern configuration capable of generating large crystal grains may exist occasionally, but it is impossible to monocrystallize any island of semiconductor layer.
Another prior art method for manufacturing a semiconductor device is reported in an article "Use of selective annealing for growing very large grain silicon on insulator", Appl. Phys. Lett. 41 pp 346 (1982), by J. P. Colinge et al. According to this method a strip type antireflection film made of silicon nitride is produced by depositing a poly-silicon layer on the entire surface of a silicon wafer, and irradiated by a laser by scanning along the strip so as to monocrystallize the entire surface thereof.